There are significant advantages to using compressed air engines over internal combustion engines. Compressed air as a fuel is relatively unlimited in availability compared to hydrocarbon-based fuels such as coal, natural gas, oil, and their derivative products. The latter fuels also have by-products as a result of their extraction and use that adversely affect the environment. Further, internal combustion engines that burn hydrocarbon fuels are very inefficient. The efficiency of an internal combustion engine powered vehicle has been estimated at less than ten percent based on energy delivered to the drive train wheels (see Efficient Use of Energy, K. W. Ford, et al. (eds.), American Institute of Physics (New York), p. 99-121).
Compressed air engines are well known in the art. Several exemplary configurations of compressed air engines are disclosed in U.S. Pat. Nos. 3,693,351; 3,765,180; 3,980,152; 4,104,955; 4,014,172 4,018,050; 4,370,857; 6,367,247; 6,508,324; 6,629,573; 6,862,973; and 7,315,089; the complete disclosures of which are incorporated herein in their entireties by specific reference for all purposes.
However, the energy density of compressed air is substantially lower than hydrocarbon-based fuels. Currently known compressed air engines with compressed air stored in reasonably-sized containers at reasonable pressures provide only a short time of operation before needing recharging (i.e., they have a short charge range), which is not practical or useful for motor vehicles with the current wide-ranging applications and demands. Longer periods of operation using the prior art require either a much larger volume of compressed air, or air stored at extremely high pressures, neither of which are practical or useful solutions.
These and other drawbacks are seen in the few air-powered cars now available in the marketplace. These cars are of much lighter weight and much smaller than typical internal combustion vehicles, which can result in safety issues on the road. The reduced mass, which may be as much as 80% less, is necessary to increase the charge range. These vehicles also have stated charge ranges of from 40 to 150 miles, with lower-speed “in-town driving” suggested or required to reach this advertised charge range. This is a function of the amount of energy required to overcome air drag, which increases with velocity, which prevents these use of these vehicles for longer trips at higher speeds.
Accordingly, what is needed is a compressed air engine and system that can deliver the power of an internal combustion engine with a charge range comparable to an internal combustion engine powered vehicle. It is to such a need that the present invention is directed.